Tuning arrangement for radio receiving sets



Nov. 10, 1936.

w. HUBER ET AL. 2,060,216

TUNING ARRANGEMENT FOR RADIO RECEIVING SETS Filed Aug. 16, 1954 I INVENTOR$ WALTER 16 1/55? Patented Nov. 10, 1936 UNITED STATES TUNING ARRANGEMENT FOR RADIO RECEIVING SETS Walter Huber and Hans Otto Roosenstein, Berlin, Germany, assignors to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application August 16,

1934, Serial No. 740,096

In Germany August 26, 1933 4 Claims.

It is known to provide scale or dial arrangements for broadcast receiver sets and the like in which the stations to be received are arranged in predetermined groups, say, according to countries, provinces, transmitter or program qualities or the type of program, and for each station group whose constituents may be distributed ad libitum over the respective wave length range, there is provided a preferably replaceable dial having an indicator device common to all of the groups.

When tuning there will naturally appear upon a group scale not only such transmitters or stations as are included in this particular group, but also those stations that are located between them. To obviate this inconvenience it has been suggested to provide filter or damping means so that the reproduction or reception of such stations as are not contained in the group will be prevented, regardless of the setting of the transmitter group.

It has also been suggested to provide on the setting device, say, on the indicator hand, a clip connected with the grid of one tube and which is in frictional engagement with the ground coat of the supporting means of the scale group. On this coat, at suitable points, recesses are provided which have the purpose of discontinuing the grounding of a grid by the aid of the condenser whenever tuning has been eifected to a transmitter station contained in the respective group. Discontinuance of the grounding is effected suddenly i. e., when the contact clip slips from the solid coat portion to a portion free from coat. For a better understanding of our invention, reference is made to the accompanying drawing in which,

Fig. 1 shows a response curve of a receiver in which the tuning operation is arranged to eifect an abrupt change in the response,

Fig. 2 shows the type of response curve obtained with a device constructed according to our invention,

Fig. 3 is a schematic diagram illustrating our invention as applied to a radio receiver and,

Figs. 4 and 5 are partial front and sectional views of a second embodiment of our invention.

Fig. 6 is a side View of a portion of the band D of Fig. 3 and its cooperating parts on an enlarged scale and,

Fig, '7 is a horizontal section through the plate P and band D of Fig. 6.

Fig. 1 shows schematically at what points of the tuning scale the receiver is ready for operation. Considering that the indicator hand moves along the line a, b, while tuning, as the tuning approaches one of the three stations 0, reception suddenly changes from zero to maximum. Even if the end or power tube were controlled by the aid of these means, which, as will be remembered, contributes but little to the overall gain, disagreeable crackling noises will manifest themselves both by the sudden grounding and the ceasing of the ground connection.

According to this invention the control of the reception is chosen in such a way that it will change in a steady or gradual manner whenever the tuning point is approached or receded from, as diagrammatically shown in Fig. 2.

For carrying this idea into practice, recourse may be had to a great number of embodiments. One of the possible schemes is schematically shown in Fig. 3. In this instance, a Wheatstone bridge W comprising four condensers C is provided between the antenna A and the first receiver circuit B. In coupling relationship with the antenna coil is the coil L arranged in the diagonal of the bridge, while another inductance coil L" is coupled with the inductance coil of the circuit B across the other diagonal of the bridge. The end of the coupling coil L is grounded. The four arms of the Wheatstone bridge consist of the four condensers Cl, C2, C-3 and C--4, though C--l and C-2 may be replaced by resistances. C-4 is the capacity between the scale group support D consisting of metallic band or the coat of a scale group support (cellon, film and the like) consisting of insulation material and the small metallic plate P coupled with the index hand of the tuner of the receiver. D is shown in the drawing in the form of a band or tape wound on the spools R. The size of the four bridge condensers is so chosen that a bridge balance is established whenever the plate P happens to be at points which are located intermediate between the'tuning points corresponding to stations included in the chosen transmitter group. At the places at which tuning takes place to one of the stations included in the group of transmitters that has been chosen, the state of balance is disturbed, and the radio frequency energy is transferred from the antenna to the first or input oscillation circuit 13. The strip 2| of the scale group sup-- port D which represents the cooperating or counter coat to the mobile plate or coat P has recesses or gaps 20 in the metallic coat 2! at the tuning points, so that the capacity P to ground at those places diifers from adjoining places. As shown more fully in Figs. 6 and '7, on the band D is shown one group of station transmitters or names N. The band is formed of an insulation layer 22 and the rear metallic face 2! which is provided with an opening or recess 20 corresponding to each desired station position. The movable plate P may be moved across the line of recesses 20 by any desired means mechanically connected to the tuning means. As shown, the plate P is carried by a flexible band or cord S operating over the pulleys 23 either of which may be mechanically connected to the receiver tuning means by any means well known to those skilled in the art. In the position shown in Figs. 6 and '7, plate P is over the metallic coating 2| and the bridge circuit is balanced so that no signal energy is transmitted to input circuit B. As plate P moves over a recess 20 the capacity between? and coating 2| changes gradually, as shown in Fig. 2, until the peak position is reached at'which maximum energy is transferred to circuit B.

The arrangement as just described is intended merely to serve as an example of applying the basic idea of the invention by the aid of a variable capacity. It would be self-suggestive to use the variable capacity, say, also for detuning a sensitive circuit, i. e., for disturbing synchronism.

In the case of heterodyne receivers the variable capacity could serve, for instance, also as a neutralizing condenser in the oscillation stage, with this result that on leaving the tuned points (0 Figs. 1 and 2), neutralization is occasioned so that the receiver is rendered inoperative or ineffective.

Attention may be specially drawn to this fact that in an arrangement according to the above described example, operation according to Fig. 2 is insured, for upon approach of the tuning point, the capacity C4 varies steadily from crest to minimum.

Another instance of embodiment of the invention is schematically illustrated in Figs. 4 and 5. Referring to Fig. 5, n: denotes the front panel of the receiver set which has an opening y. In the rear of the latter is visible the scale band D Wound on spools R. This band bears imprints of the nature of transmitter group scales. The tuning is rendered visible by moving a transparent strip e which is coupled with the tuning means and which is here shown in section at right angles to the plane through the drawing. In the tape 6 which is posteriorly blackened, is an opening 1 through which light issuing from a luminous source g is allowed to fall upon the film tape D. For this purpose, it is necessary to produce by the aid of a cylinder lens h, the image of a slit 1' upon the film tape D. Only a small section of this slender line of light extending throughout the entire width of the scale passes through the aperture 1 upon the scale D. With this movement of the opening 1 during the tuning operation there is shifted also the luminous point or spot and this indicates the position of the tuning means.

In Fig. 4 is shown aplan view upon the opening y in the front panel of the receiver set. One looks upon a transmitter group that has just been chosen and the designation of which is imprinted at I. Reference character 2 denotes the designations of the three transmitters contained in this group. Extending over the whole scale is a narrow slit 3 which has enlargements 4 at points where tuned condition to the respective transmitters occurs. The image of the slit 2' which would be thrown upon the scale support D if the tape e were imagined to be absent is indicated by the shaded rectangle 8 which extends over the whole scale. small part of the light is thrown upon the scale by tape e with the aperture f formed therein. The spot thus produced has the shape of a doubly shaded (cross hatched) rectangle 5. Of the latter, only the blackened part 6 becomes visible between the tuned points and in this way the position of the tuning means at any given However, only a time is marked or identifiable. The tuning when attained is rendered more distinctly in the form of an enlarged spot.

The tape D is posteriorly provided with a refleeting coat which has the recesses above described i. e., narrow slit 3 and enlargements 4. Outside the tuned points, as will thus be seen, only a part of the light (according to spot 6) will pass through the scale, whereas another part according to the shaded portions 1 is reflected and is brought to act upon a light responsive cell It. The effects thus produced, as well known, serve for the control of the reception. For instance, the damping of a highly sensitive circuit may be raised, or else the shift of the working point of an amplifier tube into regions of lower gain may be effected. If the effects obtainable with the light responsive cell k are too feeble, they may be reinforced or amplified, for which purpose either distinct amplifiers are used or else tubes are employed which are designed for multiple utilization operating on the reflex principle and which exist in the receiver.

In an arrangement cited as the second example a condition may be obtained that only upon the tuning to one of the stations contained in the transmitter group, reception will be feasible, and that the graph indicated in Fig. 2 is realized.

What we claim is:

1. In combination, a radio receiver having an input circuit including tuning means for tuning said circuit to a predetermined frequency, a source of radio frequency signal energy, means coupling said source to said input circuit and including a normally balanced Wheatstone bridge, and means connected to said tuning means ar ranged to unbalance said bridge in response to adjustment of said tuning means to effect reso nance of said input circuit at said predetermined frequency.

2. In combination, a tunable input circuit, a source of signal energy, a circuit coupling said input circuit to said source comprising a normally balanced Wheatstone bridge, at least two arms of said bridge having capacity reactance and one of said arms comprising a movable element mechanically connected to the adjustable tuning means of said input circuit.

3. In combination, an input circuit having an adjustable tuning means, a source of signal energy, a circuit coupling said input circuit to said source comprising a Wheatstone bridge at least two arms of said bridge consisting of condensers, one of said condensers comprising a metallic band and a plate connected to said adjustable tuning means.

4. In combination, an input circuit having an adjustable tuning means, a Wheatstone bridge, a reactor coupled to said input circuit and having its ends connected to a pair of conjugate neutral points of said bridge, a reactor having its ends connected to the other pair of conjugate neutral points of said bridge, and means for impressing signal voltages on said last named reactor, one arm of said bridge comprising a metallic film and a plate mechanically connected to said tuning means and movable adjacent said film.

WALTER HUBER. HANS OTTO ROOSENSTEIN. 

